Post hoc analysis of optimal timing of adjuvant chemotherapy after colorectal cancer surgery

There is no consensus on the optimal timing of adjuvant chemotherapy after colorectal cancer surgery. Post hoc analysis of the multinational phase 3 SCOT trial included 5719 patients undergoing curative surgery for high-risk stage II or III colorectal cancer. The analysis found that starting adjuvant chemotherapy 6 or more weeks after surgery was associated with worse 5-year disease-free survival rate (73.2%; 95%-CI 72.0-74.5) than starting adjuvant chemotherapy earlier (78.0%; 75.3-80.8). In adjusted Cox regression analysis, start of adjuvant chemotherapy greater than 6 weeks after surgery was associated with worse disease-free survival (HR 1.24; p=0.01). Timing of adjuvant chemotherapy had no significant impact on adverse events. The authors conclude that among patients undergoing curative surgery for high-risk stage II or III colorectal cancer, starting adjuvant chemotherapy more than 6 weeks after surgery was associated with worse disease-free survival.